Dexter, Inc. was incorporated in its home state. It expanded substantially and now does 20% of its business in a neighboring state in which it maintains a permanent facility. It has not filed any papers in the neighboring state. Which of the following statements is correct?

a. Since Dexter is a duly-incorporated domestic corporation in its own state, it can transact business anywhere in the United States without further authority as long as its corporate charter so provides.

b. As long as Dexter's business activities in the neighboring state do not exceed 25%, it need not obtain permission to do business in the neighboring state.

c. Dexter must create a subsidiary corporation in the neighboring state to continue do do business in that state.

d. Dexter is a foreign corporation in the neighboring state and as such must obtain a certificate of authority or it will not be permitted to maintain any action or suit in the state with respect to its intrastate business.